Answer: leguminous plants.
- A leguminous plants
- B the cereal crops
- C the tall grasses
- D the woodland ferns
Correct answer: A. leguminous plants
Explanation: Rhizobium lives symbiotically in the root nodules of legumes.
Atmospheric N₂ is fixed into ammonia by nitrogen-fixing bacteria (protected from oxygen by leghaemoglobin in root nodules), converted to nitrate via nitrification for plant uptake, and eventually returned to the atmosphere as N₂ via denitrification, completing the cycle.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.